The present invention relates to a method and apparatus for making flat bottom plastic bags and in particular to a flat bottom bag having a bottom of more than one thickness and being reinforced.
In a co-pending application, Ser. No. 376,112, filed on July 3, 1973, now U.S. Pat. No. 3,916,770 there is disclosed a flat bottom bag formed of paper, plastic, cloth or combinations thereof in which a tubular length of material is first gusseted along two sides, cut into a predetermined length and provided with seal transverse to its length. Thereafter, a mandrel is inserted in the tube to shape the bag and flatten the bottom end into a reinforced multiple layer flat bottom. The present invention has as its main object the provision of an improved method for forming the bags disclosed in the aforementioned application and simple apparatus for carrying out the method in a continuous cyclical operation.
It is a further object of the present invention to provide a method and apparatus particularly adapted to the formation of thin walled plastic bags having flat bottom. In general, in the known prior art the formation of flat bottomed bags from thin walled plastic material was most difficult and virtually impossible wherein it was necessary to form the flat bottom with multiple reinforced layers sealed together to form the unitary structure. Substitute measures were only possible in the prior art. In particular, the prior art utilized separate reinforcing layers, such as heavy cardboard to maintain a flat rectangular bottom. More often than not, the flat bottomed construction required the creation of perforations or slits in order to create the necessary folds to establish the flat condition. The present invention has as its object the formation of an imperforate reinforced construction capable of carrying solids, granular and liquid materials. In general, the known apparatus for forming bags, particularly from plastic material, are complex and rather costly both to build and to operate, in addition to being incapable of making the flat bottom imperforate bag desired herein. It is accordingly another object of the present invention to provide simple economic apparatus for the formation of such bags.
The foregoing objects, as well as further objects, features and advantages of the present invention, will be more fully appreciated by reference to the following disclosure.